How Cross-Tying During Transport Affects Horses

Reprinted from The Horse Report with permission from the Center for Equine Health, School of Veterinary Medicine, University of California, Davis (UC Davis).

Transport stress has long been thought to predispose horses to respiratory disease. The stress response during transport causes changes in serum cortisol concentrations, heart rate, immune parameters, and serum muscle enzyme activities. Another variable in the transport of horses—cross-tying—has been the subject of concern to UC Davis Center for Equine Health researchers.

While cross-tying horses individually in stalls is common practice for transporting show and race horses, horses also travel in small groups or individually without being restricted by tying.

Carolyn Stull, MS, PhS, and Anne Rodiek, MS, PhD, recently conducted a study to examine the specific physiological responses of horses during transport to either cross-tying or traveling loose. They found that the cross-tied horses had larger increases of selected stress parameters 24 hours following transport than did horses traveling loose without being tied. In particular, they found that levels of serum cortisol, which is secreted during stressful situations, were greater in the cross-tied horses, although the levels returned to normal following transport.

Cortisol also affects other physiological responses, such as the neutrophil:lymphocyte (N:L) ratio, which could be a more reliable indicator of chronic stress than cortisol. A substantial increase in N:L ratio was seen in the cross-tied horses compared with the loose horses. Neutrophilia, indicated by an increased N:L ratio, has been associated with respiratory disease in horses following long-term road transport.

Other studies have found that elevation of the horse’s head, which restricts the range of neck movements, compromises the immune system and increases the number of bacteria in transtracheal aspirates. The increase in bacteria is thought to be the result of a decrease in clearance rate of the bacteria from the tracheobronchial secretions in horses that are confined and unable to lower their heads. This information suggests that the practice of cross-tying could, along with other factors, predispose horses to respiratory disorders following transport. It also leads to further questions on the athletic potential and disease susceptibility of the horse during the recovery period and post-transit complications from other stressors such as social stress, thermal stress, and housing or pathogen challenges.

In view of these findings, Stull and Rodiek recommend that a small box stall is preferable to cross-tying during long-distance road transport. “If you have to use cross-ties or a trailer design that keeps horses’ heads elevated, unload every 6 to 8 hours to let them move around, graze, and rest,” advises Stull. And if you use a commercial carrier to ship a horse across the country, “pay the extra amount to get a box stall. It will be worth it when your horse arrives less stressed and ready to compete.”

For air transport, cross-tied restraint is still largely used to prevent the horse from damaging the integrity of the pressurized cabin. In this case, the benefits of restraint outweigh the risks.